Fluorinated polymers typically are made up of recurring monomeric units, each monomeric unit including a monomeric backbone portion attached to a perfluoroalkyl side chain. The side chain typically includes a hydrocarbon spacer group that links the side chain to the backbone portion, as well as a terminal hydrophobic perfluoroalkyl tail attached to the spacer group. The stable and inert terminal perfluoroalkyl tail is nonpolar, as well as hydrophobic and oleophobic. Thus, the fluorinated polymers may be mixed with an inert carrier or dissolved in a solvent and applied to a hydrophilic material such as paper, cloth, metals, glass or ceramic to impart to the material water and oil repellency.
The fluorinated polymer can be applied to a substrate surface by, for example, spraying, impregnation, and other methods known in the art of coating. When the fluorinated polymer is applied to the substrate, CF3 tail portions projecting perpendicular to the solid/air interface can create a low surface energy on the substrate, provided that they can be aligned in the proper fashion.
Conventional perfluoroalkyl side chains generally have the formula CnF2n+1—(CH2)m— where n typically ranges from 6 to 12, and m typically ranges from 1 to 10. It has been postulated that adjusting the number of —CH2— groups in the spacer group, as well as the number of carbon atoms in the CnF2n+1 perfluoroalkyl tail, can result in the alignment of the side chains in the polymers, which in turn results in the formation of crystalline-like regions when the polymer is applied to a substrate. However, in synthesizing conventional fluorinated polymers, the perfluoroalkyl chain length is the only part of the side chain selected to enhance formation of crystalline regions, which is believed to result in close packing by alignment of the side chains.
Preferred commercial products typically include at least about 6 to 12 fluorinated carbons (n≧6) to achieve spontaneous crystallization of the perfluoroalkyl tail portions of the side chains at the application temperature, typically about room temperature. A terminal perfluoroalkyl side chain with n≧6 has been considered necessary to render both hydrophobic and oleophobic the perfluoroalkyl tail of the fluorinated polymeric compound.